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Directions: The Building Envelope Breakdown

Written by Heidi Schwartz. Posted in Bonus Features, Construction & Renovation, Exteriors, Magazine, Special Reports, Topics

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Published on May 08, 2005 with No Comments

By Mark K. Howell
From the May 2005 issue of Today’s Facility Manager

The issues that facility managers face today are increasingly complex—especially when something goes wrong. While there is no substitute for getting an outside professional involved in the diagnosis and repair of a structural problem—be it leaks, deterioration, or other scenarios that pose a potential threat to the safety of the occupants-an understanding of the building envelope will pay dividends in determining the optimal solution.

A key ingredient to this approach is a thorough review of the essential components that comprise a building, including wall systems, roofing, and below-grade waterproofing. By examining the way a building was designed and constructed, as well as the repairs that have been made during its lifetime, facility managers can help pinpoint the sources of many problems.

Do Wall Systems Hold Up?

An important element when determining the source of a problem is the wall system. For it to function as intended, several factors must be taken into consideration, including the selection and design of compatible materials and systems, proper detailing of material junctions and terminations, installation and inspection of these details during construction, the ability of composite envelope systems to function during weather cycles, and proper maintenance by facility managers. Even the slightest difference between the way a wall system was designed and how it was actually constructed can have a major impact on performance.

Unfortunately, the amount of detail shown on drawings does not always provide sufficient instructions regarding intersections, terminations, and penetrations of wall systems, resulting in field personnel having to make educated guesses. This scenario is especially true in the construction of cavity walls, where there is zero tolerance for error in the design and construction of wall systems. In most circumstances, any design or field detailing error will result in water infiltration or even more serious failures resulting from infiltration.

A wall system’s design can be categorized into two main distinctions: barrier walls or water managed walls. Barrier walls use a blocking or interrupting mechanism to prevent the movement of water to the interior of the building. Mass barrier walls rely on sufficient thickness to prevent infiltration; face sealed barrier walls depend on the exposed exterior wall surface. With face sealed barrier walls, all joints and interfaces must be sealed to provide this exterior barrier.

Whereas barrier walls are designed to keep out water entirely, water managed walls allow for the control and discharge of anticipated amounts of water. Drainage walls include a cavity incorporated into the wall system that catches water and flushes it to the exterior. When constructing drainage walls, special care must be taken to avoid bridging the interior and exterior wall.

Maintenance: Key To Proper Performance

Proactive maintenance should encompass four main components: annual maintenance budget, regular building condition assessments, annual proactive maintenance, and seasonal visual inspections. Integrating maintenance funding into the yearly budget is essential for those committed to a property over the long-term, and a regular review of the building’s condition is a way to assess the remaining life expectancy of the materials. This is the only way for tasks such as sealant replacement, window glazing, painting, coatings, and more to be integrated into the budget.

Visual seasonal inspections should include drains, gutters, and downspouts. In areas of seasonal change, it is important to perform these inspections after every major weather event.

In addition to planned maintenance repair work, capital renewal funding should be set aside for existing structures separately from new construction. When proactive maintenance isn’t enough, it’s time for reactive measures.

Stopping Leaks

Certain processes should be followed when investigating a leak. These seven steps (based on ASTM E2128, Standard Guide for Evaluating Water Leakage of Building Walls) provide a simple, yet consistent process.

Step 1: Review project documents. Locate drawings, specifications, and other pertinent project information from the original construction materials to determine the intended design of the building. Change orders can be particularly helpful, as they tend to highlight problem areas.

Step 2: Evaluate the design concept. Review the drawings in order to understand the wall system application and how the building was intended to manage water and/or moisture. There are three main ways in which building systems can become wet: when moisture enters from the interior, when moisture enters from the exterior, and when the assembly starts out wet as a result of using wet materials or building under wet conditions.

In addition, this moisture can be removed from the exterior or interior in three ways: liquid flow due to gravity (drainage), air movement (ventilation), or vapor diffusion (vapor pressure difference). All of these mechanisms can act independently or in combination to dry out the substrate.

Step 3: Determine the building’s service history. Review previous repair attempts, work orders, or reports to uncover any faulty repairs.

Step 4: Visually inspect the building. Start at the roof and work from top to bottom to develop an informal visual survey of the structure. Take pictures of the details: penetrations, parapet walls, flashing, mechanical curbs, copings, roof cants, and weep holes. Also, document the damage to the interior of the space. Review discrepancies between the visual survey and the original design.

Step 5: Perform investigative tests. Testing provides an opportunity to recreate leakage and water paths under controlled conditions. Non-destructive testing involves methods that simulate either surface flow or wind driven rain.

Surface flow can be simulated by wetting a wall area with a matrix of uniformly spaced spray nozzles that deposit a full film of water though a soaker hose (a trickle of water from an ordinary hose also is suitable). If surface flow alone is not enough to determine the cause of the leak, wind driven rain can be simulated using a pressurized chamber that is sealed to the wall test area.

If these testing methods prove ineffective, destructive testing may be necessary. Although destructive testing allows for the determination of the damproofing or flashing condition (both of which are designed to divert the water to the exterior) the amount of this testing should be limited, because the process may expose mold and bring an entire additional element to the investigation.

Step 6: Analyze the findings. Analyze the gathered information and determine the effectiveness of the design concept and any attempted repairs. Is there a life safety concern? Was mold or mildew found? Can any further tests clarify the analysis?

Step 7: Prepare a report. Present the information gathered from the previous steps in a walk through format, including photographs and solutions for fixing the leak.

Facility managers armed with this knowledge about their facilities have the opportunity to implement long-term solutions that will likely save money and time when compared to quick fix solutions. Following these steps will enable managers to create a more efficient, durable, and cost-effective facility for everyone to enjoy for years to come.

Howell is employed by Structural Preservation Systems (www.structural.net) in Baltimore, MD. 

About Heidi Schwartz

Heidi Schwartz

Schwartz joined Group C Media in April 1989 as managing editor of Today's Facility Manager (TFM) magazine (formerly Business Interiors) where she was subsequently promoted to editor/co-publisher of the monthly trade magazine for facility management professionals. In September 2012, she took over the newly created position of internet director for TFM's parent company, Group C Media, where she is charged with developing content and creating online strategies for TFM and its sister publication, Business Facilities. Schwartz can be reached at schwartz@groupc.com.

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